Let's Make Robots!

IR compound eye

Mr._General_4.bas17.21 KB
Vendor's Description: 

I have posted some tip/walkthroughs on home made IR sensors for obstacle detection and later for motion tracking. Now DAGU proudly presents the IR compound eye. Designed to fit LMR's universal sensor bracket, this sensor works by shinning IR light onto an object and then tracking the reflected IR. This sensor does not work in bright daylight as sunlight has a lot of IR and blinds the sensor.The IR LEDs can be controlled by a digital output so that ambiant light as well as reflected light can be measured. Your microcontroller needs 4 analog inputs available to use this sensor. See a video of it working here: http://www.youtube.com/watch?v=iKYCob7getU

Note: calibration is not normally required, heatshrink is provided fo those who wish to fine tune their eye. A black permanent marker can also be used. Incorrect application can reduce the range of the eye.

This product is now sold at Robot Shop.

Click on the schematic for a bigger image.



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Is there a way to measure-thingy test an IR phototransistor?

I didn't add the corner edge detector bits (yet anyway) so I have 4 of the phototransistors remaining. I've got no problem swapping one of those in, I'd just like to be able to verify which one is bad, and know that the one I'm putting in is good (if it's indeed a wonky part issue).

I put these ones on a multimeter set to diode test and got readings from 0 to off the scale. At this point I have not determined the exact problem. It may be a PCB fault.

At any rate you need 8 good ones for the eye and it is just as easy for me to send you a new fully assembled and tested board as it would be for a few parts.

Once I work out the problem I'll let you know.

Playing with my Mr. General kit today. Thanks OddBot!!!

I'm having a similar sounding problem as Wntrmute. I have verified I hooked pin1 to 5v and pin 7 to GND. I just keep on having the "top" receptors (Q7 Q8) giving me values around half of what the others do. No amount of tweaking heat shrinks has gotten that one to play nicely.

Here's a screenshot of the fake-o-scope showing at first the ceiling (6 feet + away), and then a white object at 100mm.  The white trace is analog 0 on my Arduino, which is Q7-Q8. *edit* Oh, and the 4 IR leds were indeed on at the time of capture.
(click for larger version)

Photos of the board itself are available here, 2 to 3 MB each, please forgive the flash burn. The later ones are a bit better looking than the first ones.

Any ideas?

I would say you have put too much heat on one of the 2 photo transistors for the top sensor. Because these are being soldered flat on the board it is very easy to damage them. With a batch of about 10 made by another assembler here I found similar problems.

I ended up soldering another one up myself and it works ok although the new batch do seem more sensitive than the previous batch.

In future we may get these PCBs machine made as they are easy to damage.

Cool, thank you for looking into this. I'm not surprised that it's likely I overcooked something I just had no idea how to prove it. I'll desolder and swap in a new one from my leftovers.


Hi Oddbot, I've hooked up one of these to my board but without success... from three of the output pins I get readings of around 4800mv, but the other gives me 50mv; none of fitting heatshrink, toggling the input to pin 6, or waving objects in front of the sensor have any effect. Am I missing something obvious here?

Sounds strange. Assuming you have the power connected the right way with +5V to pin 1 and ground to pin 7 then regardless of pin 6 being high or low you should get variable reading as you move your hand within 100-200mm of the eye. Best results with pin 6 high.

Sounds like maybe some components have been put in the wrong way or damaged by heat during soldering. Can you post a closeup photo?


Based on the other posts I think I'm seeing the problem, which I have the pin order reveresed; I assumed 'J1' was labelling pin 1 rather than the block of pins. That'd explain why one pin wasn't reading anything, as it was actually the digital in not an analog out. Let's hope I've not toasted the board...
...and having wired it up correctly it seems to work now!

hi could you tell me what sort of range the sensor can detect objects